Generally, conventional automatic transmissions include a torque converter to transfer engine torque from an engine to an input of the transmission, planetary gearsets that provide various gear ratios of torque and thus various drive speeds, and fluid pressure-operated, multi-plate drive or brake clutches and/or brake bands that are connected to the individual elements of the planetary gearsets in order to perform gear shifts between the various gear ratios.
In addition, conventional automatic transmissions include one-way clutches (i.e., overrunning clutches) that cooperate with the multi-plate clutches to optimize power shifts and a transmission controller for selectively applying and releasing elements to shift the gears. For example, the controller chooses the proper gear depending on system conditions such as the shift-program selected by the driver (i.e., Drive, Reverse, Neutral, etc.), the accelerator position, the engine condition, and the vehicle speed.
As an accelerator is further depressed, and the vehicle increases speed, the controller disengages appropriate clutches to sequentially shift up through each of the gears until the highest gear is engaged. Specifically, the controller initiates a “single swap” event that releases an engaged clutch and applies an idle clutch such that a shift from a lower gear to a higher gear is accomplished. As can be appreciated, as the releasing clutch loses capacity, the applying clutch picks up capacity simultaneously such that a driver does not notice or feel the gear shift.
Once the highest gear is engaged, further depression of the accelerator will cause the controller to operate another single swap event such that a lower gear is chosen, and a requisite torque is supplied by the transmission. In this manner, the controller will downshift through the gears sequentially, each time applying and releasing a single pair of clutches to perform the requisite gear shift.
Conventional shift sequences adequately shift between respective gears of a transmission by applying and releasing a single pair of multi-plate clutches, as previously discussed. However, when shifting from an overrunning clutch to a multi-plate clutch, a smooth transition generally depends solely on the applying element. Ideally, when the multi-plate clutch is applied, torque will be dropped off the overrunning clutch and transferred to the applying clutch to achieve a smooth transition between gears. However, timing application of the multi-plate clutch is often a difficult task for conventional transmissions and transmission controllers.
Therefore, a transmission capable of timing the application of a multi-plate clutch following release of an overrunning clutch to effectuate a smooth gear shift is desirable in the industry. Furthermore, a transmission capable of learning a fill volume for an applying multi-plate clutch assembly to time the application of the multi-plate clutch assembly with the release of an overrunning clutch is also desirable.